package org.apache.lucene.analysis.sa;

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;
import java.io.Reader;
import java.io.File;
import java.io.FileReader;
import java.nio.charset.StandardCharsets;
import java.util.Map;
import java.util.HashMap;

import org.apache.lucene.analysis.miscellaneous.SetKeywordMarkerFilter;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.analysis.util.CharArraySet;
import org.apache.lucene.analysis.util.StopwordAnalyzerBase;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.core.LowerCaseFilter;
import org.apache.lucene.analysis.core.StopFilter;
import org.apache.lucene.analysis.in.IndicNormalizationFilter;
import org.apache.lucene.analysis.in.IndicTokenizer;
import org.apache.lucene.util.Version;
import org.apache.lucene.analysis.util.WordlistLoader;
import org.apache.lucene.analysis.compound.SandhiCompoundWordTokenFilter;
import org.apache.lucene.analysis.compound.DictionaryCompoundWordTokenFilter;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;

/**
 * Analyzer for Sanskrit.
 * <p>
 * <a name="version"/>
 * <p>You must specify the required {@link Version}
 * compatibility when creating SanskritAnalyzer:
 * <ul>
 *   <li> As of 3.6, StandardTokenizer is used for tokenization
 * </ul>
 */
public final class SanskritAnalyzer extends StopwordAnalyzerBase {
  private final CharArraySet stemExclusionSet;
  public static CharArraySet dict = null;
  
  /**
   * File containing default Sanskrit stopwords.
   * 
   * Default stopword list is from http://members.unine.ch/jacques.savoy/clef/index.html
   * The stopword list is BSD-Licensed.
   */
  public final static String DEFAULT_STOPWORD_FILE = "stopwords.txt";
  private static final String STOPWORDS_COMMENT = "#";
  
  /**
   * Returns an unmodifiable instance of the default stop-words set.
   * @return an unmodifiable instance of the default stop-words set.
   */
  public static CharArraySet getDefaultStopSet(){
    return DefaultSetHolder.DEFAULT_STOP_SET;
  }
  
  /**
   * Atomically loads the DEFAULT_STOP_SET in a lazy fashion once the outer class 
   * accesses the static final set the first time.;
   */
  private static class DefaultSetHolder {
    static final CharArraySet DEFAULT_STOP_SET;

    static {
      try {
        DEFAULT_STOP_SET = loadStopwordSet(false, SanskritAnalyzer.class, DEFAULT_STOPWORD_FILE, STOPWORDS_COMMENT);
      } catch (IOException ex) {
        // default set should always be present as it is part of the
        // distribution (JAR)
        throw new RuntimeException("Unable to load default stopword set");
      }
    }
  }
  
  /**
   * Builds an analyzer with the given stop words
   * 
   * @param version lucene compatibility version
   * @param stopwords a stopword set
   * @param stemExclusionSet a stemming exclusion set
   */
  public SanskritAnalyzer(Version version, CharArraySet stopwords, CharArraySet stemExclusionSet) {
    super(version, stopwords);
    this.stemExclusionSet = CharArraySet.unmodifiableSet(
        CharArraySet.copy(matchVersion, stemExclusionSet));
  }
  
  /**
   * Builds an analyzer with the given stop words 
   * 
   * @param version lucene compatibility version
   * @param stopwords a stopword set
   */
  public SanskritAnalyzer(Version version, CharArraySet stopwords) {
    this(version, stopwords, CharArraySet.EMPTY_SET);
  }
  
  /**
   * Builds an analyzer with the default stop words:
   * {@link #DEFAULT_STOPWORD_FILE}.
   */
  public SanskritAnalyzer(Version version) {
    this(version, DefaultSetHolder.DEFAULT_STOP_SET);
  }
	

  /**
   * Creates
   * {@link org.apache.lucene.analysis.Analyzer.TokenStreamComponents}
   * used to tokenize all the text in the provided {@link Reader}.
   * 
   * @return {@link org.apache.lucene.analysis.Analyzer.TokenStreamComponents}
   *         built from a {@link StandardTokenizer} filtered with
   *         {@link LowerCaseFilter}, {@link IndicNormalizationFilter},
   *         {@link SanskritNormalizationFilter}, {@link SetKeywordMarkerFilter}
   *         if a stem exclusion set is provided, {@link SanskritStemFilter}, and
   *         Sanskrit Stop words
   */
  @Override
  protected TokenStreamComponents createComponents(String fieldName,
      Reader reader) {
    final Tokenizer source;
	
    if (matchVersion.onOrAfter(Version.LUCENE_3_6)) {
      source = new StandardTokenizer(matchVersion, reader);
    } else {
      source = new IndicTokenizer(matchVersion, reader);
    }
	  
	if (dict == null) {
		Reader freader = null;
		try {
			dict = new CharArraySet(matchVersion, 2000, true);
			freader = IOUtils.getDecodingReader(SanskritAnalyzer.class.getResourceAsStream("dictionary.txt"), StandardCharsets.UTF_8);
			dict = WordlistLoader.getWordSet(freader, dict);
		} catch(Exception e) {
			System.out.println("dictionary for sanskrit not found");
		}
		finally {
			try {
				IOUtils.close(freader);
			} catch(Exception e) {
				;
			}
		}
	}
	
		  //TokenStream result = new LowerCaseFilter(matchVersion, source);
	TokenStream result = new StopFilter(matchVersion, source, stopwords);
	result = new SandhiCompoundWordTokenFilter(matchVersion, source, dict);
		  // if (!stemExclusionSet.isEmpty())
		  //result = new SetKeywordMarkerFilter(result, stemExclusionSet);
	result = new DictionaryCompoundWordTokenFilter(matchVersion, result, dict, 8, 4, 20, true);
    //result = new IndicNormalizationFilter(result);
    result = new SanskritNormalizationFilter(result);
    result = new StopFilter(matchVersion, result, stopwords);
    //result = new SanskritStemFilter(result);

    return new TokenStreamComponents(source, result);
  }
}
